checkCIF procedure

PLAT791

 A tentative (R/S) assignment is done on the basis of the geometrical and   
 atom type data in the CIF. A correct assignment depends on the algorithm   
 used to automatically detect double and triple bonds. For that reason it is
 important that the molecule is complete (i.e. all hydrogen atoms should be 
 included). In case of a chiral molecule in a centro-symmetric spacegroup, it
 is essential that the coordinate set used and the associated molecular
 (ORTEP) illustration are consistent. This can be verified by checking the  
 identical signs of relevant torsion angles. The absolute structure assignment
 should also be consistent with the lowest value of the Flack parameter and/or
 known absolute configuration.